Author

Date of Award

2014

Degree Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Lindon Young, PhD

Second Advisor

Qian Chen, PhD

Third Advisor

Farzaneh Daghigh, PhD

Fourth Advisor

Marcus G Bell, PhD

Abstract

ESWL is an effective, non-invasive therapy utilized to fragment stones in the kidney and subsequently be cleared in the urinary tract. Although lithotripsy provides a safer alternative to invasive treatments for removing stones, ESWL may cause vasoconstriction after ESWL treatment, reducing renal blood flow, which can cause kidney damage leading to acute to chronic hypertension clinically. This may be due to kidney vascular endothelial dysfunction, which is characterized as increased oxidative stress and decreased endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) bioavailability. We hypothesized that ESWL would decrease NO and increase hydrogen peroxide (H2O2) in rat renal veins. Rats given tetrahydrobiopterin (BH4), the essential cofactor of eNOS coupling, would cause a decrease in H2O2 release and increase in NO release compared to ESWL + saline controls. On the contrary, when dihydrobiopterin (BH2), the cofactor for eNOS uncoupling, is given at the end of ESWL treatment we predict an increase in H2O2 release and decrease in NO release compared to ESWL + saline controls. Blood NO and H2O2 were directly measured in real-time by inserting a microsensor into the left renal vein in the anesthetized rat. ESWL treatment consisted of 1,000 shocks for approximately 13 minutes. Saline or drug was injected via the jugular vein immediately post-ESWL and at the same time point for the non-ESWL controls. ESWL + saline controls (n = 5; p< 0.01) had significantly increased H2O2H2O2 release compared to the non-ESWL controls (n = 5) and NO release in ESWL + saline rats (n = 5; p< 0.01) was significantly decreased compared to non-ESWL controls (n = 6) from 5- v 30 mins post-ESWL. In ESWL+BH4 rats (n=5), H2O2 released was significantly reduced from 10-30 mins compared to ESWL + saline controls (p≤ 0.05). ESWL+BH4 (n=5) also significantly increased NO release 5-30 mins compared to ESWL + saline controls (p≤ 0.01). For both NO (n=5) and H2O2 (n=5) release, the ESWL + BH2 group showed a similar decrease in NO and increase in H2O2 release to the ESWL + saline group (n=5). This may be because eNOS could be under saturated conditions with respect to BH2 levels generated by ESWL. The data shows that BH4 significantly reduces H2O2 and increases NO, thereby promoting eNOS coupling. This results in increased NO bioavailability and decreased oxidative stress on the renal microvasculature.